Read each sentence to find out whether there is any grammatical error in it. The error, if any will be in one part of the sentence. The letter of that part is the answer. If there is no error, the answer is 'D'. (Ignore the errors of punctuation, if any).

1. It is an established fact that the transcendental American poets and philosophers.
2. who lived in the latter half of the nineteenth century.
3. were more influenced by Indian philosophy, in particular by Upanishadic Philosophy.
4. No error.